Abstract: Considering all types of structures used for shore protection purposes, the groin is probably the most widely used and yet it is perhaps the one structure least understood. Groins or groin systems of a particular design may be found where the intended purpose was achieved; however, it is not uncommon to learn of other cases where a similar design was used and negligible benefits resulted. Basically, the function of a groin is to build or maintain a protective beach by trapping littoral drift (beach materials) or to retard the erosion of an existing beach. A lack of understanding of all factors affecting the functional and structural design of groins has led to seemingly endless variations in groin design. This lack of understanding is directly related to the paucity of established theoretical or empirical relationships between the functional behavior of groins and the environmental factors in which the structures must exist. The purpose of this presentation is to point out pertinent features of basic types of groins and to illustrate some of the many variations which have been built in the United States.